(1) Field of the Invention
The present invention relates to porous spherical silica or silicate granules and to a process for the production thereof. More specifically, the invention relates to true spherical porous granules of silica or silicate of a metal of Group II of periodic table, and to a process for the production thereof. The invention further relates to functional fillers such as an anti-blocking agent, a deodorizing agent, an odor scavenging agent and a sweat-controlling agent composed of the above spherical silica or silicate granules, that can be used for resins, fibers, paints and cosmetics.
(2) Description of the Prior Art
As fillers of the amorphous silica type, there have been known so-called dry-type silica and wet-type silica. Depending upon the properties, they have been used for such applications as paints, papers for recording information, rubbers, resin molded products and the like. The former silica is obtained by decomposing SiCl.sub.4 in the flame of oxygen and hydrogen, has a small granular size and a spherical shape, and has a relatively small surface activity that stems from specific surface area, pore volume, pore distribution, etc. On the other hand, the latter silica is obtained by neutralizing alkali silicate with an acid, and generally has a large granular size and a wide granular size distribution, but its interior is porous and exhibits a relatively large surface activity. Thus, amorphous silica exhibits properties that greatly vary depending upon the preparation method. In the case of the latter wet-type silica, in particular, the reaction conditions such as concentration, pH, temperature, pressure and time for neutralizing alkali silicate with an acid can be variously changed, making it possible to obtain amorphous silica having widely different properties.
Among the amorphous silica fillers, it has been urged to provide amorphous silica granules of a regular shape such as fine spherical silica granules since they do not coagulate among the filler granules and exhibit excellent dispersing properties in the resins. Fine spherical silica granules have heretofore been produced by a method in which organic silane is hydrolyzed in an organic solvent such as ethanol, a method in which a silica sol or gel is formed in a spherical shape, a method in which a W/O emulsion is prepared from an aqueous solution of alkali silicate and an organic solvent followed by hydrolysis, a method in which molten silica is formed in a spherical shape, and a method in which granules of various kinds of zeolites of a regular shape are treated with an acid. According to these methods, however, the starting materials are expensive, and the aforementioned demand is not fully satisfied.
U.S. Pat. No. 4,752,458 discloses a process for producing fine spherical silica by adding a solution of an acid to a solution of soluble silicic acid and further adding thereto an organic polymer solution of an alkali metal salt of alginic acid, an ammonium salt of alginic acid, a starch, a gelatin, a pectin, or a mixture thereof prior to forming a gel thereof.
It has further been attempted to blend various blending agents such as inorganic fillers comprising various silicates in addition to those of silica in order to impart a variety of functions to the resin molded articles such as films and the like. The blending agents can be roughly divided into those for improving chemical properties of the resins and those for improving physical properties of the resin molded articles. The former agents include a heat stabilizer which suppresses the hydrogen chloride-removing reaction of chlorine-containing polymers and a stabilizer which suppresses the deterioration caused by a catalyst residue of a halogen compound contained in olefin type resins, and the latter agents include an anti-blocking agent for preventing the stretched resin film from being blocked and an agent for removing odor from a resin.
It has long been known to use silicates such as calcium silicate as a blending agent for improving chemical properties or a blending agent for improving physical properties. For instance, Japanese Patent Publication No. 32899/1977 discloses blending a chlorine-containing polymer with a synthetic calcium silicate as a thermostabilizer.
Moreover, Japanese Patent Laid-Open Publication No. 15237/1992 discloses a blending agent for resins comprising a fine crystalline calcium silicate hydrate.
Japanese Patent Laid-Open No. 10019/1986 discloses that a synthetic fine crystalline zinc silicate of the sauconite type, hemimorphite type or willemite type is useful as a blending agent for developers and resins.